JPS61283121A - Charged beam projecting exposure device - Google Patents

Abstract

PURPOSE:To enable accurately the contracted image of a mask pattern to be transferred on a sample surface at high speed by providing an electro-optical system having a mask stage for placing a mask, a sample stage for placing a sample and a unit for scanning a charged beam on the mask. CONSTITUTION:An electron beam 21 from an electron gun 20 is emitted through emitting lenses 22, 23, a beam forming aperture 24 to a mask 6 on a mask stage 26. The electron beam image of the mask 6 is projected as a contracted image on a sample 14 through a contracting projection lens 29 to print (draw) a pattern. A large deflector 25 scans a beam on the mask 6. The emitting position is corrected by a small deflector 27 in the scanning step. The deflector 27 is used to small-deflect to scan the mask. The pattern is drawn on the entire surface of the sample while moving the stage 26 and a sample stage 31. In this case, the moving error is corrected by information of a mask stage laser length measuring unit 46 and a sample stage laser length measuring unit 48.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus that uses an electron beam to transfer a reduced image of a mask pattern onto a sample surface at high speed and with high precision for manufacturing semiconductor LSIs and the like. It is something.

[Conventional technology]

Conventionally, a device that uses photoelectrons generated from a mask to transfer a mask pattern onto a sample (wafer) using an electron beam for manufacturing semiconductors such as LSI (hereinafter referred to as "optoelectronic drawing device") There is also a device (hereinafter referred to as a "hole mask drawing device") that irradiates a hole mask (shadow mask) with an electron beam and forms an image of the electron beam on the sample surface. The photoelectron imaging device is, for example, a J.P. Scott 1:1 Electron Image Projector.

Solid State Technology15, 1977
(J, P, 5cot, Electron Image
Projector, 5solidState Tech
Nology/May, 1977). This uses a special electron optical system that superimposes a uniform magnetic field and a uniform electric field to irradiate all of the generated photoelectrons onto the sample surface.The current density is extremely low and the energy This solves the problem of photoelectron sources with large dispersion.

However, this method had the following drawbacks.

(a) Patterns cannot be reduced, which is becoming increasingly necessary as patterns become finer. Even if an attempt was made to do this by adding a reduction optical system, only a very small number of photoelectrons could be used due to the aberrations of the electron optical system, resulting in an extremely low productivity.

Mountain) The shape of the projected figure cannot be corrected. Furthermore, since the current density for mark detection is low, highly accurate alignment drawing cannot be performed.

(C) The life of the photoelectron generating section is short.

For example, the hole-opening mask writing device is described in Etchi Boren et al., High Throughput Submicron Lithography with Electron Beam Proximity Printing, Solid State Chikunoroshii/September,
L 984 (H, Bohlen et al, Hi
gh Throughput Submicron L
ithography with Electron
Beam Proximity Printing, 5
olid 5tate Technology/5ep
te+nber, 1984). This will be explained with reference to FIGS. 6 to 9.

Figure 6 shows the electron optical system, where 1 is an electron gun, 2 is an irradiation lens, 3 is an electron beam, and 4 is a large deflector (aligner).
, 5 is a small deflector (small aligner), 6 is a pattern mask,
7 is a mask holder. Here, the electron beam 3 that irradiates the mask 6 is a parallel beam as shown, and the large deflector 4 scans this beam beam on the mask 6. During scanning, by slightly changing the inclination of the beam bundle using the small deflector 5, the shape of the projected figure on the mask can be slightly changed. This is shown in FIG. Figure 7 (al is X.

This is an example in which a pattern is drawn without any change in position in both Y directions. By linking this with scanning in the Y direction and changing the irradiation position only in the X direction, as shown in Figure 7 (
It is possible to transform the projected figure from bl to (f). By superimposing changes in the irradiation position in the Y direction on these, more complex deformations can be realized. FIG. 8 shows an example of a mask used in this technique and its pattern transferred onto a sample surface. In FIG. 8(a), 10 is a mask pattern, 11
is a mark (hole mark) in the mask 6, and in FIG. 8(b), 12 is an alignment mark on the surface of the sample 14,
13 are 10 projected figures onto the surface of the sample 14.

When drawing, after positioning the sample 14 at a predetermined position, the large deflector 4 directs the beam beam onto the mark 11 in the mask 6, and then the small deflector 5 scans the alignment mark 12 with a small amplitude. Perform one mark detection.

Repeat this action 4 times. As a result, the sum of the amount of deformation of the sample surface region corresponding to the projected figure 13 and the amount of deformation of the shape of the mask pattern 10 itself is determined. Using this data, patterns are drawn while correcting the irradiation position as described in FIG. 7 so that each pattern on the mask 6 is accurately projected at the desired position on the sample surface. This drawing may be performed by using a large deflector 4 so that the beam beam scans the entire surface of the mask pattern 10. After this operation, the sample 14 is moved and the same operation is repeated to complete pattern drawing on the entire surface of the material as shown in FIG.

In addition, in this technique, for a donut-shaped mask pattern, the above-described pattern drawing is repeated twice using a pair of complementary masks 15 and 16 as shown in FIG. 9(a). The complete pattern 17 shown in b) is transferred. Although this method doubles the number of drawing operations, it is easier to manufacture the mask 6 than the conventional method of supporting the inside of the donut with a fine mesh, and there is no beam scattering at the mesh. At this stage, complementary masks are superior in practical terms.

As mentioned above, this hole mask lithography system can transfer patterns with higher current density and productivity compared to photoelectronic lithography equipment, and the current density during mark detection is also higher, so it is possible to transfer patterns at high speed and with high precision. It has the advantage of being able to detect marks and accurately correcting complex deformations of the mask and sample.

[Problem that the invention seeks to solve]

However, this perforated mask drawing apparatus has the following drawbacks.

■Patterns cannot be reduced.

■The deflection area of the large deflector 4 needs to be at least as large as the area of the LSI chip, and this deflection increases aberrations in each part of the electron optical system, and in this respect, the transfer of semiconductor patterns is becoming increasingly finer. cannot respond to

■Since the beam position during mark detection is the corner of the chip that is farthest from the beam axis, there is a deterioration in mark detection accuracy due to loss of symmetry of the backscattered electron detector signal.

[Means for solving problems]

In order to eliminate such drawbacks, the present invention provides an electron optical system having a mask stage on which a mask is mounted and a sample stage on which a sample is mounted.

Furthermore, a device is added to the electron optical system described above to scan the mask with a charged beam while continuously moving the mask stage and sample stage.

[Effect]

In the present invention, the charged beam reduced image of the mask pattern is pattern-transferred, and at the same time, during the transfer operation, the shape of the reduced figure is transferred while being corrected so that it becomes the desired figure. Further, during the drawing operation, drawing is performed while continuously moving the mask and the sample.

〔Example〕

FIG. 1 shows a first embodiment of the present invention, in which 20 is an electron gun, 21 is an electron beam, 22 is a first irradiation lens, 23 is a second irradiation lens, 24 is a beam shaping aperture, and 25 is a mask. A large deflector as a device for scanning with a charged beam,
26 is a mask stage, 27 is a small deflector, 28 is a focus correction lens, 29 is a reduction projection lens, 30 is a detector for sample surface height and reflected electrons, 31 is a sample stage, and 32 is an electron optical system. Further, 40 is a control computer, 41 is a lens power supply, 42 is a large deflection control circuit, 43 is a stage control unit,
44 is a control circuit for the sub-deflection/correction lens, 45 is a signal processing circuit, 46 is a laser length measuring device for mask stage, 47 is a mask stage driving device, 48 is a laser length measuring device for sample stage, 49 is a specimen stage driving device It is. In FIG. 1, the same or equivalent parts as in FIGS. 6, 8, and 9 are given the same reference numerals.

Prior to explaining the operation of the apparatus configured in this way, the operation of the electron optical system 32 will be explained with reference to FIG.

In FIG. 2, 50 is a beam shaping lens.

The electron beam 21 from the electron gun 20 is transmitted through an irradiation lens 22.
At step 23, the beam becomes a parallel beam with a predetermined distribution and irradiates onto the beam shaping aperture 24. Beam shaping aperture 2
The beam beam passing through the aperture 4 is transferred to the mask stage 2.
The mask 6 on the mask 6 is irradiated. The current density at this time is controlled by changing the diameter of the beam bundle. The mask 6 is a perforated mask (shadow mask). A reduction projection lens 29 projects the electron beam image of the mask 6 onto the sample 14 as a reduction image, thereby printing (drawing) a pattern. In this embodiment, the reduction ratio of the reduction projection lens 29 is 1/2 and 1/4.
Stage switching is possible.

The large deflector 25 scans the beam over the mask 6.

Accordingly, the irradiation beam on the surface of the sample 14 also scans an area corresponding to the reduction ratio. During this scanning process, the small deflector 27 is used to correct the irradiation position. For this purpose, a correction method similar to that explained in FIG. 7 is used. Further, a small deflector 27 is also used for small deflection for mark scanning. A reflected electron signal at that time is obtained using the detector 30. Note that instead of directly irradiating the mask 6 with the electron beam 21 that has passed through the beam shaping aperture 24, an aperture image of the beam shaping aperture 24 may be projected onto the mask 6 using the beam shaping lens 50.

From the above, it has been found that by using the electron optical system 32 in this example, a reduced image of the scanning area of the mask 6 can be drawn on the surface of the sample 14. The following operations are required to draw the pattern of the entire area of the mask 6 over the entire area of the sample with high precision.

■Correction of deflection distortion of the deflector ■Measurement and correction of distortion (deformation) on the sample surface■Drawing of the pattern on the whole surface of the sampleHere, the drawing of the pattern on the whole surface of the sample in (■) is performed using the control computer 4.
0 under the control of the mask stage control section 43 under the control of the mask stage drive device 47. Sample stage drive device 49
This is done while moving the mask stage 26 and sample stage 31 using the mask stage laser length measuring machine 46. Information from the laser length measuring device 48 for the sample stage is used. Below, each operation will be explained in the order of (1), (2), and (2) above.

■Correction of deflection distortion: A method for correcting deflection distortion of a large deflector will be explained using Fig. 3. In FIG. 3, 100 is a standard pattern (opening) provided in the mask 6, and its image 110 is projected onto the surface of the sample 14. In FIG. 3, the same or equivalent parts as in FIG. 1 are given the same reference numerals. First, as shown in FIG. 3 (al), the standard pattern 100 is positioned on the beam axis by the mask stage controller 43, and the large deflector 25 is used to scan the standard pattern 100 with a small amplitude.

At the point when the electron beam 21 crosses over the standard pattern 100, the detector 30 obtains a reflected electron signal, and therefore uses the scanning signal and the signal obtained by the detector 30 to determine the beam axis (in the same manner as normal mark detection). The precise positional relationship with the standard pattern 100 can be known. This measurement value M1 and the length measurement information L1 of the mask stage laser length measurement device 46 at that time
The control computer 40 stores this. Next, as shown in FIG. 3(b), the standard pattern 100 is moved by a predetermined distance, and the length measurement information L2 of the mask stage laser length measurement device 46 at that time is obtained. The electron beam 2 is controlled by the large deflector 25.
1 is deflected by a distance of J=L2-L1+M1, and the aforementioned small amplitude scanning is performed on the standard pattern 100 to accurately measure the deviation M2 between the beam deflection position and the standard pattern 100. Here, the deviation M2 is the deflection distortion when deflecting by a distance l. The deflection distortion is corrected by measuring such deflection distortion at a plurality of measurement points and correcting the deflection data of the large deflector based on the measurements.

Correction of deflection distortion of small deflectors is a well known fact. That is, this is carried out by locating the standard mark at multiple locations on the surface of the sample 14, detecting the standard mark each time, and measuring the deflection distortion using the length measurement information of the laser length measuring device 48 for the sample stage at that time. do.

As described above, it was possible to correct the deflection distortion of the large and small deflectors 25 and 27 based on the laser coordinate system.

■Oki and correctness of distortion (゛) on test 2 surface: Explain using Figure 4. To detect the upper left chip mark, mask pattern 1 is used as shown in FIG. 4(a).
Align mark 11 within 0 and mark 12 with electron beam 21
on the beam axis. If the reduced image of the mark 11 is aligned and has the same shape as the mark 12, the two will overlap with each other with a deviation corresponding to the chip distortion.

Here, the image of the mark 11 in the mask pattern 10 is scanned with a small amplitude using the small deflector 27 (mark scanning), and the amount of deviation is measured. At the same time, the height detector in the detector 30 detects the height of the area around the alignment mark 12.

Next, to detect the chip mark on the upper right, see Figure 4(b).
As shown in the figure, the upper right mark 1 in the mask pattern 10
1 and the alignment mark 12 are positioned on the beam axis of the electron beam 21 and the above operation is repeated. The above steps are repeated for four chip marks to measure the deformation of the chip on the sample surface.

Using this measurement data, a highly accurate alignment drawing operation is performed while correcting the irradiation position using the small deflector 27 during pattern drawing, which will be described next.

■Pattern drawing on the entire surface of the sample: Figure 4 (C1 to (kl) will be used to explain.
350 shown in Figures (d) and fk) is the mask stage 26
and sample stage 3I (hereinafter referred to as “stage”)
This is a unit drawing area that is drawn by repeating continuous movement, steps, and repeats, and 400 shown in FIG. ) shown in 410
indicates repeat drawing by one continuous movement of the stage, and 420 shown in FIGS. 4(f) to (1) is an arrow indicating the direction of the area that expands as the drawing progresses on the sample surface at this time, 430 and 440 shown in FIG. 4(f) are an electron beam irradiation area and an electron beam scanning path. Figure 4 (
C) is the mask pattern used in this example, and Fig. 4 (
In C1, 6 is a mask, 10 is a mask pattern, 1
1 is a mark.

At the beginning of the drawing of the unit drawing area 350 in FIG. 4(d), the fourth
As shown in the figure (el), the marks are detected one after another in the order of the path 400, and finally the stage is positioned at the continuous movement drawing start point. Figure 4 (dl, (Ql
, 12 is a mark, 13 is a projected figure of a mask pattern, and 14 is a sample. Next, as shown in FIG. 4(f), the stage is moved while scanning the electron beam 21 on the mask 6 using the large deflector 25. At this time, the moving speed of the sample stage 31 is M times that of the mask stage 26 (M is the reduction ratio of the reduction projection lens 29), and the moving directions are different from each other. The stage movement error is measured in real time by a laser length measuring machine 46 for the mask stage and a laser length measuring machine 48 for the sample stage, and the results are transmitted to the beam position via the large deflector 25 and the small deflector 27. As a result, the irradiation positions on the mask 6 and the sample 14 are sufficiently accurate. Note that the scanning direction of the electron beam 21 on the mask 6 is approximately perpendicular to the moving direction of the stage 1, and the stage speed is set according to the irradiation time of the electron beam 21. Therefore, the amount of correction based on the laser values of the large deflector 25 and the small deflector 27 only needs to be corrected for the speed fluctuation of the stage. Figure 4 (gl, (hl)
The figure shows how drawing is performed under this continuous movement.

That is, the electron beam 21 is scanned over the mask 6 in the θ direction, while the mask 6 and the sample 14 are sent in the direction of the arrow 421. As shown in FIG. 4 (hl), after a certain period of time, the area scanned by the mask 6 and the area drawn by the sample 14 are enlarged. The area is drawn.Next, as shown in FIG. 4(1), the moving direction of the stage is reversed and the drawing operation is performed under the same continuous movement.The above operation is repeated to draw the unit drawing area 350. During this drawing process, the deformation of the sample in the
Correct using 7.

An example of a correction formula is shown below.

x=Lx+M(to182 ・X+A3 ・Y+
A4 ・XY)y=Ly+M(B1+B2
-X+B3-Y+B4-XY) Here, X and Y are the coordinates on the mask pattern 10, and x and y are the correction amount corrected by the deflection of the small deflector 27 (represented by the coordinates of the sample 14). Further, Lx and Ly are laser feedback amounts, Ai and Bi are correction coefficients for alignment (correction of deformation of the mask 6 and sample 14), and M is a reduction ratio of the reduction projection lens 29.

In addition, the focus position of the beam is corrected in real time using a focus correction lens 28 shown in FIG. 1 according to the deformation of the sample in the height direction (Z direction). As a result of the above, fine patterns can be drawn with high precision without depending on the deformation of the sample surface. After finishing the drawing of the unit drawing area 350, the drawing operation of the next unit drawing area starts.

Repeat the above steps to finish drawing the entire surface of the sample.

Next, an example of drawing using a complementary mask will be described.

In this example, (451°452) and (451°452) shown in FIG.
Using a complementary mask consisting of a 2m mask pattern of (453, 454), first, (451, 452)
Drawing is performed in accordance with the area of the unit drawing area 350. Next, move the stage and use (453, 454),
Drawing is performed again on the same unit drawing area 350 to transfer a complete pattern.

FIG. 5 shows a second embodiment of the invention. In this embodiment, three electron optical systems 32 are arranged in parallel, and a mask 6 and a sample 14 are installed in each of them. Here, only one stage each is required for the mask 6 and the sample I4. Furthermore, since the lenses and deflectors are of electrostatic type, only one driving circuit is required. What is provided for each electron optical system is the second irradiation lens 23. Small deflector 27. Focus correction lens 28. This is a control or drive circuit for the detector 30.

In the pattern drawing, from the measurement of the deformation of the sample surface described in the first embodiment, the entire surface of the sample is drawn simultaneously using each electron optical system. As a result, the processing time per sample is reduced to 1/3.

The first and second embodiments have been described above, and the effects of these embodiments are as follows.

-Since it is possible to reduce the projection of LSI patterns, it can support future miniaturization of LSI patterns.

(2) Since there is no need to increase the amount of beam deflection during writing, it is possible to reduce the aberration of the electron optical system and obtain a large beam current value, allowing fine patterns to be processed at high speed.

- Since multiple electron optical systems can be created by adding a small number of components, it is possible to shorten the drawing time and the time required for measuring sample surface deformation, etc.

Note that although the explanation so far has been made using an electron beam, an ion beam may be used instead of the electron beam. That is, in this embodiment, various charged beams can be used.

〔Effect of the invention〕

As explained above, the present invention provides an electron optical system having a mask stage on which a mask is mounted and a sample stage on which a sample is mounted.
By adding a device that scans the mask with a charged beam while continuously moving the mask stage and sample stage, the following effects are produced.

■Since the pattern can be projected in a reduced size, it is possible to draw fine patterns.

■Since the mask and sample each have a stage, productivity is not compromised even if the amount of deflection for pattern drawing is small.As a result, the charged beam current can be increased and the charged beam has a small blur. Since a projected image can be obtained, fine patterns can be drawn with high productivity.

■ Highly accurate pattern writing is possible by measuring the movement distance of both the mask and sample stage with a laser length measuring machine and feeding the results back to the charged beam irradiation position of the mask and sample. Since the continuous movement direction and the mask scanning direction are substantially perpendicular, the amount of correction of the charged beam irradiation position with respect to stage movement can be small.

■If chip mark detection is performed directly below the beam axis, highly accurate mark detection is possible, and as a result, highly accurate pattern writing is possible.

■Since multiple electron optical systems are installed, it is possible to reduce dead time such as mark detection time in addition to pattern drawing time.

[Brief explanation of drawings]

FIG. 1 shows a first diagram of a charged beam projection exposure apparatus according to the present invention.
FIG. 2 is a configuration diagram showing the electron optical system, FIG. 3 is an explanatory diagram for explaining the method of correcting deflection distortion, and FIG. 4 is a diagram showing the correction method for deflection distortion. An explanatory diagram for explaining the method of measurement and correction and the method of drawing a pattern on the entire sample surface, FIG. 5 is a configuration diagram showing a second embodiment of the charged beam projection exposure apparatus according to the present invention, and FIG. A configuration diagram showing a conventional electron optical system. Figure 7 is a pattern diagram showing an example of pattern drawing in a conventional electron optical system. Figure 8 shows an example of transferring a mask and its pattern onto a sample surface using a conventional device. Pattern Diagram, FIG. 9 is a pattern diagram showing an example of transfer using a set of complementary masks in a conventional apparatus. 6... Mask, 14... Sample, 20... Electron gun, 21... Electron beam, 22° 23... Irradiation lens, 24... Beam shaping aperture, 25・
...Large deflector, 26...Mask stage, 27.
...Small deflector, 28...Focus correction lens, 29.
...Reducing projection lens, 30...Detector, 31...
...Sample stage, 32...Electron optical system, 40...
...Control computer, 41...Lens power supply, 42...
...Large deflection control circuit, 43...Mask stage control section, 44...Sub-deflection/correction lens control circuit, 4
5... Signal processing circuit, 46... Laser length measuring machine for mask stage, 47... Mask stage driving device, 48... Laser length measuring machine for sample stage, 49...
...Sample stage drive device, 50...Beam shaping lens.

Claims (5)

[Claims] (1) A charged beam projection exposure apparatus that projects a pattern image using a charged beam is equipped with an electron optical system that has a mask stage on which a mask is mounted and a sample stage on which a sample is mounted, and is capable of producing a reduced image of a pattern at high speed. A charged beam projection exposure device that is characterized by highly accurate projection. (2) A charged beam projection exposure apparatus according to claim 1, wherein there is a plurality of electron optical systems. (3) A charged beam projection exposure apparatus according to claim 2, wherein the electron optical system has a common mask stage and a common sample stage. (4) In a charged beam projection exposure apparatus that projects a pattern image using a charged beam, a mask stage on which a mask is mounted, a sample stage on which a sample is mounted, and the mask stage and the sample stage are continuously moved. 1. A charged beam projection exposure apparatus comprising an electron optical system having a device for scanning a mask with a charged beam while the mask is being exposed, and projecting a reduced image of a pattern at high speed and with high precision. (5) A charged beam projection exposure apparatus according to claim 4, characterized in that there is a plurality of electron optical systems.